Theres a few companies in the US that do "screw kits" for between £9 to 13" P&P, I've had some from Teamfasteddy (stainless steel) for my BJ4 and there 4-40s, I know others that have used Tonys Screws and rcscrewz and been happy with them. Thats if you don't mind importing gear. Not sure if they do steel, but might be worth asking anyway.
www.teamfasteddy.com
www.tonysscrews.com
www.rcscrewz.com